Cr Bain said the NZTA would likely have greater capacity to make improvements to SH15, the subject of a recent emergency community meeting where residents clamoured for a speed limit reduction.
"It's a complicated process to have a speed limit reduced," Cr Bain said.
"But there will be some changes in regards to safety and we're in discussions [with NZTA] all the time."
In May, more than 150 Otaika Valley Rd and Mangakahia Rd residents gathered at a meeting after a spate of trucks rolling over in the region, two of which happened on Otaika Valley Rd. They shared stories of what it was like living on the busy logging route, which serviced about 25 per cent of Northland's production forests, citing noise and safety concerns.
Cr Bain said the handover was "extremely good news" and an outcome the councils had lobbied for for years.
The route would be a "boon" to for the region's economic development, he said.
"We want to see the port developed, and we've got people continually asking about putting more industry in there."
The NZTA would now provide all funding for the operation and maintenance of SH15, meaning it now managed about 877km of road in Northland. Northland councils were responsible for about 5800km of local roads.